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package client
import (
"io"
"net/http"
"sync/atomic"
)
// KeepAliveTransport drains the remaining body from a response
// so that go will reuse the TCP connections.
// This is not enabled by default because there are servers where
// the response never gets closed and that would make the code hang forever.
// So instead it's provided as a http client middleware that can be used to override
// any request.
func KeepAliveTransport(rt http.RoundTripper) http.RoundTripper {
return &keepAliveTransport{wrapped: rt}
}
type keepAliveTransport struct {
wrapped http.RoundTripper
}
func (k *keepAliveTransport) RoundTrip(r *http.Request) (*http.Response, error) {
resp, err := k.wrapped.RoundTrip(r)
if err != nil {
return resp, err
}
resp.Body = &drainingReadCloser{rdr: resp.Body}
return resp, nil
}
type drainingReadCloser struct {
rdr io.ReadCloser
seenEOF uint32
}
func (d *drainingReadCloser) Read(p []byte) (n int, err error) {
n, err = d.rdr.Read(p)
if err == io.EOF || n == 0 {
atomic.StoreUint32(&d.seenEOF, 1)
}
return
}
func (d *drainingReadCloser) Close() error {
// drain buffer
if atomic.LoadUint32(&d.seenEOF) != 1 {
// If the reader side (a HTTP server) is misbehaving, it still may send
// some bytes, but the closer ignores them to keep the underling
// connection open.
_, _ = io.Copy(io.Discard, d.rdr)
}
return d.rdr.Close()
}
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